President Michel Aoun paid a visit to Iraq on Tuesday, the first by a Lebanese head of state to the country.
He kicked off his talks with President Fuad Masum with talks focusing on the fight against terrorism.
"We had constructive talks which reflect the historical and brotherly ties that link our two countries and our people," Aoun told a joint news conference with his Iraqi counterpart.
"I would like to take advantage of this occasion to congratulate the Iraqi people for their firmness, patience and determination in the face of adversity... and terrorism," he said.
Aoun later met Prime Minister Haidar al-Abadi and other key officials. He is set to travel to Armenia on Wednesday.
Iraq has been scarred by decades of conflict.
After an eight-year war with neighboring Iran in the 1980s, and the 2003 US-led invasion, Iraq was targeted by ISIS which seized swathes of the country following a 2014 offensive.
Aoun told reporters that Lebanon, too, had suffered from the extremists but succeeded in pushing them back from a border region with Syria.
He said Arab states and the international community must build "joint efforts to fight against terrorism in an efficient and radical way, to eliminate them and end the factors that favor terrorist ideology".
He added: “Lebanon strongly supports Iraq’s unity against all plots aimed at threatening it.”
For his part, Masum described as “historic” Lebanese-Iraqi ties.
“The two countries are bound together by the respect for diversity and coexistence,” he added.
At the start of the visit, Masum surprised Aoun, a former general and army chief, with a birthday cake decorated with the Lebanese and Iraqi flags. Aoun turned 83 earlier this week.
Aoun was accompanied by cabinet ministers including the ministers of industry, interior and tourism.
